PROJECT SUMMARY Memory is the unique capacity of brain to store information for extensive periods of time, however how memories persist for decades remains unclear. The formation and maintenance of long-term memory is believed to require the synthesis of new proteins inside the neuronal synapses. Cytoplasmic Polyadenlation Element Binding (CPEB) proteins are a family of proteins critical in regulating synaptic mRNA translation. Two CPEB family members, CPEB3 in mice, and Orb2 in Drosophila Melanogaster are capable of existing in a monomeric state or oligomeric self-replicating state, properties that are unique to functional prion-like proteins. Interestingly, only the oligomeric forms of CPEB/Orb2 proteins are critical for sustaining memory, which suggests CPEB/Orb2?s amyloidogenic self-aggregating activity promotes the persistence of memory in a dominant manner once formed. Thus, the experience-dependent conversion of CPEB/Orb2 from its monomeric to oligomeric state regulates the formation of long-term memory. However, the regulation of prion- like conversion of CPEB/Orb2 is relatively unknown. Preliminary observations show that Orb2 is phosphorylated and phosphorylation regulates its stability. Intriguingly, phosphorylation also regulates Orb2?s interaction with other proteins that increase its ability to oligomerize. The central hypothesis of this proposal is that conversion of monomeric to oligomeric Orb2/CPEB is regulated by the phosphorylation. The first aim in this proposal is to identify both the kinases responsible for phosphorylating Orb2 and the residues of Orb2 being phosphorylated. The second aim is to genetically modulate Orb2?s phosphorylation state and examine how it affects Orb2 function in biochemical assays and as well as Orb2-depedent long-term memory in Drosophila. Considering aberrant conversion of pathogenic prions is a hallmark of a number of neurodegenerative disorders and is associated with memory loss, a greater understanding of the cellular mechanisms regulating conversion of functional prion-like proteins may provide important insight for controlling amyloid production of different prion and prion-like proteins.